Selfing mutants from heterothallic strains ofPhysarum polycephalum

Abstract

SUMMARYPlasmodial formation in the myxomycetePhysarum polycephalumis controlled by a mating type (mt) locus, with heterothallic amoebae normally being unable to form plasmodia in pure clones. We report the isolation by mutagenesis of selfing mutants from heterothallic strains, and their analysis. Various amoebal strains of different mating types were mutagenized with a range of mutagens, and a number of selfing mutants (designated Het−) were isolated. A specific sensitivity ofmt2amoebae to mutagenesis by NMG was observed. This sensitivity segregated as a single locus closely linked or allelic to themt2locus. When the Het−clones were incubated at 30 °C, selfing was greatly inhibited. This property was used to determine themtspecificities of four Het−clones. The process of plasmodial induction in pure clones ofCLwas also studied using the 30 °C temperature effect.